An agricultural combine is a self-propelled agricultural vehicle that is designed to perform two main functions. A first function is cutting the crop material from the field and drawing the crop material into the machine, and the second function is to separate grain or other seeds from the residue. After separation, the vehicle typically expels the residue onto the field via a back end of the vehicle while the grain or seeds are stored and periodically unloaded from the vehicle.
The threshing of the crop material is typically conducted by introducing the crop material into a threshing drum. This threshing drum is provided with threshing slats that rotate directly above a concave. Thereby, the distance between the threshing slats and concave is adaptable, for example by movably mounting the concave in the agricultural vehicle. Due to the rotation of the slats, and the distance between the slats and the concave, crop material is beaten and squeezed so that grain or seeds are released from the residue. In this context, it will be understood that crop material comprises a combination of grain or seeds and residue. This technique of threshing is well known and widely adopted in agricultural combines, and is therefore not described in more detail in the present description.
Particularly when grain is harvested, the beating and the squeezing of conventional threshing drums and concaves tend to crack and split a significant percentage of the grain. Cracking and splitting of the grain damages the outer shell of the grain. As a result of this damaged shell, grain is significantly more susceptible to fungus. Recent studies have shown that fungus on grain may develop toxic substances in the grain. Due to these toxic substances in the grain, the value of the grain substantially decreases when a higher percentage of the grain is cracked and split.